New possibilities for controlling gas nitriding process by simulation of growth kinetics of nitride layers

This paper presents results of computerised simulations of the gas nitridin g process, demonstrating the influence of the nitriding potential of NH3-H- 2 atmosphere on the composition and growth kinetics of gamma' and epsilon n itride layers on pure iron. For the simulation, the recently developed K-N- T phase diagram and growth kinetics models for both phases were utilised, a s well as the latest results of experimental research. Simulation results i ndicate optimum possibilities of process control far the formation of layer s of predictable phase composition, thickness of particular zones, and surf ace nitrogen concentrations. Also included are data on growth kinetics of t he nitride layer (epsilon/gamma' and alpha zones) on alloy steels. The role of nitride forming and other alloying elements in process kinetics is disc ussed.